Addition Of Pore-forming Agent Research Articles

Fabrication of high-performance recrystallized silicon carbide ceramic membrane based on particle packing optimization

Overcoming the challenges associated with achieving high uniformity and connectivity of pore channels in ceramic membranes, we designed silicon carbide ceramic membrane derived from the recrystallization process based on the Dinger-Funk equation of the closest-packing model with various grain grading. Furthermore, the effects of particle size distribution on the resulting microstructure and pore architecture of the ceramic membrane was also explored. The findings corroborated the critical importance of raw material particle size distribution in controlling pore size distribution and morphology. After sintering at 1900°C, the silicon carbide ceramic membrane, benefiting from ideal particle packing, exhibited a remarkably uniform pore structure. Notably, the most probable pore size constituted over 70 %, while achieving an open porosity of 51.3 % even without the addition of pore-forming agents. The silicon carbide ceramic membrane also demonstrated exceptional hydrophilicity (water contact angle:∼0°), impressive water permeation (1210 L m−2 h−1·bar−1), coupled with efficient turbidity removal (∼100 %) in carbon black wastewater treatment applications. Additionally, membrane regeneration proved effective using a dilute NaOH solution backwash, achieving a flux recovery efficiency of 98 %. This strategy had directive significance for designing high-performing silicon carbide ceramic membranes.

Hydroxyapatite/Poly (Butylene Succinate)/Metoprolol Tartrate Composites with Controllable Drug Release and a Porous Structure for Bone Scaffold Application.

Nowadays, it is a challenge for a bone scaffold to achieve controllable drug release and a porous structure at the same time. Herein, we fabricated hydroxyapatite/poly (butylene succinate)/metoprolol tartrate (HA/PBS/MPT) composites via melt blending, aiming to provide the option of an in situ pore-forming strategy. The introduction of HA not only significantly improved the hydrophilicity of the PBS matrix by reducing the hydrophilic contact angle by approximately 36% at a 10% content, but also damaged the integrity of the PBS crystal. Both were beneficial for the penetration of phosphate-buffered saline solution into matrix and the acceleration of MPT release. Accompanied with MPT release, porous structures were formed in situ, and the HA inside the matrix was exposed. With the increase in HA content, the MPT release rate accelerated and the pore size became larger. The in vitro cytocompatibility evaluation indicated that HA/PBS/MPT composites were conductive to the adhesion, growth, and proliferation of MC3T3-E1 cells due to the HA being exposed around the pores. Thus, the MPT release rate, pore size, and cell induction ability of the HA/PBS/MPT composites were flexibly and effectively adjusted by the composition at the same time. By introducing HA, we innovatively achieved the construction of porous structures during the drug release process, without the addition of pore-forming agents. This approach allows the drug delivery system to combine controllable drug release and biocompatibility effectively, offering a novel method for bone repair material preparation. This work might provide a convenient and robust strategy for the fabrication of bone scaffolds with controllable drug release and porous structures.

Role and Mechanism of a Micro-/Nano-Structured Porous Zirconia Surface in Regulating the Biological Behavior of Bone Marrow Mesenchymal Stem Cells.

Zirconia as a promising dental implant material has attracted much attention in recent years. Improving the bone binding ability of zirconia is critical for clinical applications. Here, we established a distinct micro-/nano-structured porous zirconia through dry-pressing with addition of pore-forming agents followed by hydrofluoric acid etching (POROHF). Porous zirconia without hydrofluoric acid treatment (PORO), sandblasting plus acid-etching zirconia, and sintering zirconia surface were applied as controls. After human bone marrow mesenchymal stem cells (hBMSCs) were seeded on these four groups of zirconia specimens, we observed the highest cell affinity and extension on POROHF. In addition, the POROHF surface displayed an improved osteogenic phenotype in contrast to the other groups. Moreover, the POROHF surface facilitated angiogenesis of hBMSCs, as confirmed by optimal stimulation of vascular endothelial growth factor B and angiopoietin 1 (ANGPT1) expression. Most importantly, the POROHF group demonstrated the most obvious bone matrix development in vivo. To investigate further the underlying mechanism, RNA sequencing was employed and critical target genes modulated by POROHF were identified. Taken together, this study established an innovative micro-/nano-structured porous zirconia surface that significantly promoted osteogenesis and investigated the potential underlying mechanism. Our present work will improve the osseointegration of zirconia implants and help further clinical applications.

Addition of Pore-Forming Agents and Their Effect on the Pore Architecture and Catalytic Behavior of Shaped Zeolite-Based Catalyst Bodies.

Porous materials, such as solid catalysts, are used in various chemical reactions in industry to produce chemicals, materials, and fuels. Understanding the interplay between pore architecture and catalytic behavior is of great importance for synthesizing a better industrial-grade catalyst material. In this study, we have investigated the modification of the pore architecture of zeolite-based alumina-bound shaped catalyst bodies via the addition of different starches as pore-forming agents. A combination of microscopy techniques allowed us to visualize the morphological changes induced and make a link between pore architecture, molecular transport, and catalytic performance. As for the catalytic performance in the methanol-to-hydrocarbons (MTH) reaction, pore-forming agents resulted in up to ∼12% higher conversion, an increase of 74% and 77% in yield (14% and 13% compared to 8.6% and 7.7% of the reference sample in absolute yields) toward ethylene and propylene, respectively, and an improved lifetime of the catalyst materials.

Boiling Heat Transfer Characteristics of Porous Microchannel with Pore-Forming Agent

Traditional microchannel needs to face the flow-reversal difficulty in high heat fluxes due to limited space. It results in large pressure and temperature fluctuation. Porous microchannels arouse more interest to provide a new solution to this problem. Flow boiling experiments in porous microchannels with PFA were investigated. Porous microchannels were sintered by 10 μm (or 30 μm) spherical copper particles with pore-forming agent (Na2CO3, 60–90 μm). Porous microchannels were composed of 23 parallel porous microchannels with 600 μm in width and 1200 μm in depth.The addition of PFA (pore-forming agent) could increase the sample porosity. For Q10 series, sample porosities increase from 20.4% to 52.9% with the PFA percentage change from 0% to 40%, while for the Q30 series they increase from 26.6% to 47.5%. Experimental results showed the boiling heat transfer coefficient (HTC) reached the maximum at the moderate porosity for both Q10 and Q30 series. Too large or too small porosity would degrade boiling heat transfer performance. It demonstrated that there existed an optimal range of PFA content for sintered microchannels. PFA content has a minor effect on the average pressure drop and would not cause the rapid increase in flow resistance. Visual observation disclosed that the sample porosity would affect the pressure instability significantly. The sample with moderate porosity showed periodic pressure fluctuation and could establish rhythmical boiling. Particle size also exerted a certain influence on the boiling heat transfer performance. Q30 series could achieve higher HTC and CHF (Critical heat flux) than Q10 series. This is attributed to the larger ratio of layer-thickness-to-particle-size (δ/d) for Q10-series samples.

Improved Photocatalytic Performance for Rhodamine B Degradation by Porous Zn2SnO4 Prepared with Carbon Black as a Pore-Forming Agent

Hydrothermal synthesis followed by a calcination step was used to prepare porous Zn2SnO4 powders using carbon black as a pore-forming agent. The porous Zn2SnO4 was used as a photocatalyst to degrade the Rhodamine B dye from aqueous solution under UV artificial light. X-ray diffraction, N2 adsorption-desorption isotherms, and UV-Vis diffuse reflectance were used to characterize the material. The addition of pore-forming agent (carbon black) did not change the crystalline structure of Zn2SnO4 phase. In addition, increasing the surface area and porosity as well as decreasing the band-gap energy was observed. The combination of these characteristics favored the photodegradation of Rhodamine B, reaching 96% of dye degradation at 15 min of reaction time. In addition, the photocatalyst was active after six cycles of reuse. Therefore, the produced material in this work showed to be a potential photocatalyst to remove Rhodamine B dye from aqueous solution.

Preparation of Lightweight Mullite-Anorthite Refractories by Different Routes

Mullite-anorthite as a kind of lightweight refractory combines the low thermal conductivity of anorthite and the excellent thermal properties of mullite. In this work, mullite beads and calcium aluminate cement was used as the main component and bonding agent. The lightweight mullite-anorthite refractory was prepared by difference routes including foaming method, addition of pore-forming agent and sacrificial template method. The phase composition, bulk density, apparent porosity and thermal conductivity of samples were compared. The results showed that anorthite formed as the consequence of the reaction of cement and mullite. Extra addition of foam, cornstarch and polyurethane sponge could decrease the bulk density of samples. The pore size of samples prepared by foaming method was the smallest. The apparent porosity of samples obtained by sacrificial template method was largest, but the thermal conductivity was the highest due to the open pores.

The cooperative utilization of imprinting, electro-spinning and a pore-forming agent to synthesise β-cyclodextrin polymers with enhanced recognition of naringin

The aim of this study was to identify if the addition of an inorganic pore-forming agent (PFA) could provide an efficient route to significantly improve the binding capacity of molecularly imprinted nanofibers (MINs), along with increasing their imprinting effect and selectivity. A non-covalently imprinted composite nanofiber (MIN–PFA) with in situ generated silica as a pore-forming agent was prepared using an electro-spinning technique with naringin (NG) as a template, β-cyclodextrin as a functional monomer, hexamethylene diisocyanate as a cross-linker, and polyvinyl butyral as an electro-spinning matrix. For comparison purposes, two imprinted polymers (MIN and MIP) were prepared in the absence of PFA, with or without electro-spinning employed. The binding properties and selectivity of the nanofibers were evaluated using equilibrium binding experiments. MIN–PFA exhibited a high specific binding capacity (∼13.0 μmol g−1) towards naringin, binding 30% and 57% more than MIN and MIP, respectively. The N2 gas adsorption isotherm at 77 K also demonstrated that the addition of PFA could enhance the surface area of the imprinted nanofibers.

Research the Performance of Alumina Insulation Material by Freeze-Drying

The traditional method of preparation alumina insulation material includes the addition of pore-forming agent, direct foaming, foam impregnation and gel-casting. In this experiment, α-alumina as raw material, silica fume as an additive, Combination freeze-drying method, add pore-forming agent and direct foaming successfully prepared low-density, high strength, low thermal conductivity of alumina insulation material. Change the particle size of pore-forming agent can be get different properties of the sample. The SEM photograph was clearly observed that the hole wall dense uniform, α-alumina particles sufficient contact, no significant ice sublimation hole left. There are also the reasons of the sample with higher value of bending strength and compressive strength. This can make a control of porosity, as well as pore size, pore shape and pores space topology of alumina insulation material.

The Porous TiNb<sub>24</sub>Zr<sub>4</sub> Alloys with Controllable Porosity Fabricated by Conventional Sintering

In the present study, porous titanium alloys were fabricated successfully by mixing titanium, niobium, and zirconium powder with pore-forming agent of ammonium bicarbonate via conventional sintering method. The pore characteristics, such as pore morphology and distribution, mean pore size and porosity of prepared porous TiNb24Zr4alloy were investigated by optical microscopy, image processing and density determination. It was found that the pore characteristics mainly depended on the shape and size of used ammonium bicarbonate particles in present study. The porosity of the alloys could be tailored by controlling the amount of ammonium bicarbonate addition. The porous TiNb24Zr4alloys were near β type titanium alloys, which consisted mainly of β phase and a little of α phase. The amount of α phase increased in the porous alloys due to segregation caused by the addition of pore-forming agent.

EFFECT OF GAS DIFFUSION LAYER CHARACTERISTICS AND ADDITION OF PORE-FORMING AGENTS ON THE PERFORMANCE OF POLYMER ELECTROLYTE MEMBRANE FUEL CELLS

The performance of five layer membrane electrode assemblies having different characteristics of gas diffusion layers was determined at 70°C cell temperature and ambient pressure. The maximum power density at 0.6 V was 0.36 W/cm2 for the membrane electrode assembly prepared with the gas diffusion layer having minimum thickness (SGL BC 30 type). On the other hand, the maximum power density at 0.5 V was 0.44 W/cm2 for the membrane electrode assembly prepared with SGL BC 34 type gas diffusion layer. It was found that resistance of a membrane electrode assembly is strongly dependent on gas diffusion layer thickness. Moreover, membrane electrode assemblies prepared with carbon paper gas diffusion layers resulted in higher performance than the assembly prepared with carbon cloth gas diffusion layer. Addition of pore-forming agents, which were ammonium carbonate, ammonium bicarbonate, ammonium sulfonate, and ammonium oxalate, to the catalyst ink lowered the performance.

Vitrocerâmicas porosas do sistema LZSA utilizando resíduos orgânicos como agentes formadores de poros

Nas últimas décadas, tem crescido o uso de cerâmicas porosas em aplicações tecnológicas, tais como filtros, suportes catalíticos, materiais para implantes ósseos e estruturais. Entre os métodos de obtenção de cerâmicas porosas, o de adição do agente formador de poros ao pó cerâmico é amplamente utilizado, devido à sua simplicidade. Visando a um reaproveitamento de resíduos orgânicos e subprodutos vegetais, este trabalho trata sobre a produção de vitrocerâmicas porosas do sistema Li2OZrO 2-SiO2-Al2O3 (LZSA) por meio da adição de bagaço da cana-de-açúcar e de pó de madeira ao pó vítreo, como agentes formadores de poros. A degradação térmica desses agentes, após calcinação/sinterização a 750 graus Celsius (°C), foi estudada por termogravimetria e espectroscopia de infravermelho. na. Avaliou-se a microestrutura dos materiais porosos por microscopia eletrônica de varredura (MEV) e foram obtidas porosidades na faixa de 49 a 73%.

Effect of pore-forming agent on PTCR characteristics of n-BaTiO3

Porous n-BaTiO3 ceramics are synthesized by the addition of pore-forming agent into the (Ba,Sr)TiO3 powder. From the DTA-TGA analysis for samples containing the PEG and corn-starch, it was found that an exotherm occurred at 262 and 315°C, respectively, weight loss commenced at 165 and 252°C, and was virtually complete by 265 and 472°C, respectively. The porosity of n-BaTiO3 ceramics increased and the grain size decreased with increasing the pore-forming agent. From the XRD analysis at high angles, all the samples with and without the pore-forming agent at room-temperature exhibit the tetragonal structure. PTCR jump of the samples containing pore-forming agent is 1-2 orders higher than that of sample without the pore-forming agent. It is also found that the development of PTCR characteristic in the porous n-BaTiO3 ceramics containing pore-forming agent is related to grain boundaries, which basically equals that in ordinary BaTiO3 without pore-forming agent, from the complex impedance results.

Preparation and swelling characterization of poly (n‐isopropylacrylamide)‐based porous hydrogels

AbstractNine different poly(n‐isopropylacrylamide)‐based hydrogels, including nonionic, cationic, and anionic hydrogels, were synthesized in with and without the addition of pore‐forming agents. The synthesized hydrogels were characterized with dry gel density measurements, scanning electron microscopy observations, and the determination of the swelling ratio swelling kinetics. All the results showed that the cationic hydrogels had faster swelling kinetics than the anionic and nonionic hydrogels. The addition of pore‐forming agents (NaHCO3 and carboxymethylcellulose) during the synthesis process led to porous hydrogels with lower dry densities, swelling ratios, and swelling kinetic parameter values. An empirical equation was developed to successfully correlate the swelling kinetic parameter with the hydrogel swelling ratio. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3651–3658, 2004